Printer and display system

ABSTRACT

The present invention is directed to a printer and display system wherein the images from an optical character generator are directed along two separate optical paths. A planar light-to-heat transducer element is positioned in one of the optical paths to intercept the generated character images for thermal printing a permanent reproduction of the intercepted characters. A visual display is positioned in the other optical path to intercept the generated character images for forming viewable images of the generated character images.

United States Patent 1191 Brown et al. Oct. 28, 1975 [5 PRINTER ANDDISPLAY SYSTEM 3,401,262 9/1968 Fergason et a1. 250/331 3,631,51212/1971 Janning 346/76 R [75] Inventors Rbert Brown 3,752,667 8/1973-Donfrio 346/76 R x James Carmen, Kettermg, 01110; 3,838,431 9 1974Germer 346/76 R Donald Churchill; Alan J. Kresch, both of AppletonPrimary Examiner-Joseph W. Hartary [73] A i NCR C ti Dayton, OhiAttorney, Agent, or Firm-J. T. Cavender; Albert L.

S l ,J Ed d D 221 Filed: May 6, 1974 65s er r .ugas [21] Appl. No.:467,417 [57] ABSTRACT The present invention is directed to a printer anddis- [52] us. C1. 346/17; 250/316; 350/160 LC; p y y m r in h im g fr man op ical h r- 354/; 346/76 R acter generator are directed along twoseparate opti- [51] Int. C1. G011) /10; B41B 13/00 l p h A pl n r ligh-h t tr ns c r el ment i [58] Field of Search... 346/17, 76 R, 107 R,110 R, positioned in one of the optical paths to intercept the 346/33 A;355/44, 45; 354/5, 6; 250/316, generated character images for thermalprinting a per- 330, 331, 332; 350/160 LC, 171, 169 manent reproductionof the intercepted characters. A visual display is positioned in theother optical path to [56] References Cited intercept the generatedcharacter images for forming UNITED STATES PATENTS viewable images ofthe generated character images. 3,252,375 5/1966 Bunting 350/171 15Claims, 12 Drawing Figures l l 4 M1 41 sx I j Sheet 1 0f 6 U5. PatentOct. 28, 1975 US. Patent Oct. 28, 1975 Sheet20f6 3,916,420

FIG. 2A

FIG. 28

FIG. 20

U.S. Patent Oct. 28, 1975 Sheet 3 of6 3,916,420

U.S. Patent Oct.28, 1975 Sheet50f6 3,916,420

FIG. 5

FIG

Sheet 6 of 6 US. Patent Oct. 28, 1975 FIG. 7

PRINTER AND DISPLAY SYSTEM BACKGROUND OF THE INVENTION In businessmachines, such as cash registers, there exists a need for providing avisual display of the price of each item and of the totals along with asales slip for use by the vendor and the customer. In the past theprinting mechanisms which prints the sales slips has beenelectromechanical in nature and has required relatively large amounts ofpower to operate. Due to recent advances in the electronic arts, therehas been a trend by business machine manufacturers towards substitutingelectronic circuits for mechanical parts whenever practical. The printersection of the business machine has been one of the mechanical unitswhich has been found to be difficult to replace. Although a variety ofelectrooptic devices, such as gaseous discharge display panels, havebeen used for the visual display, hammer type printers are stillcommonly utilized for making the permanent copies. In certain selectapplications thermal printers have been used to eliminate the mechanicalhammers. Because the driving requirements of electronic display devicesdiffer greatly from those of either the mechanical hammer printer or thethermal printer, separate driving systems have been required for each ofthese units. A system which could merge the driving requirements of theprinter and visual display while still providing a display similar tothe gas discharge or other electro-optic type displays would be highlydesirable in that such a merging would provide not only a cost reductionbut a reduction in weight and the total number of components used persystem. Additional and significant improvement is realized if the powerrequirements of the logic and control circuitry is compatible with stateof the art integrated circuits.

Examples of prior art visual display devices can be found in US. Pat.No. 3,690,745 by D. Jones, entitled Electro-Optical Devices UsingLyotropic Nematic Liquid Crystals, and in US. Pat. No. 3,703,331 by J.E. Goldmacher, entitled Liquid Crystal Display Element Having Storage.The devices of these prior art patents utilize a thin cell containing aliquid crystal. The Jones patent additionally utilizes a standard sevenbar electrode arrangement for generating numeric images. The Goldmacherdevice utilizes a matrix of elements, which matrix would theoreticallybe capable of generating both numeric and character images.

A prior art field effect liquid crystal shutter device is described inUS. Pat. No. 3,700,306 by Cartmell, et al., entitled Electro-OpticShutter Having A Thin Glass Or Silicon Oxide Layer Between TheElectrodes And The Liquid Crystal, which patent is assigned to TheNational Cash Register Company, the assignee of the present application.

The present state of the art in electronic displays has been summarizedin an article entitled Electronic Numbers authored by Alan Sobel, whichappeared in Scientific American, June 1973, Volume 228, Number 6, Pgs.6473.

A thermal type printer particularly adaptable to business machines isdisclosed in US. Pat. No. 3,631,512, entitled Slave Printing Apparatusby J. L. Janning, which patent is assigned to The National Cash RegisterCompany, the assignee of the present application. In one embodimentdisclosed in that patent, a first matrix of light sources may beselectively energized to produce a desired character pattern. A secondmatrix of semiconductor areas is positioned with respect to the firstmatrix such that each semiconductor area receives the light from acorresponding light source. Pairs of conductors, positioned on oppositeedges of each semiconductor area, sense the decrease in resistivity in alight actuated semiconductor area, causing an increased current to flowthrough the semiconductor area which increased current is used to heat aresistance element that is positioned in proximity to a thermalsensitive medium.

From the foregoing description of the prior art it can be seen that theneed exists for a business machine which uses low power and a minimumnumber of mechanical parts to provide both a visual display and aprintout.

SUMMARY OF THE INVENTION The present invention is directed to a systemhaving a printer and visual display utilizing a common optical charactergenerator for providing a temporary and a permanent record of thegenerated characters. The system is particularly adaptable for use withlow power integrated circuits.

In one preferred embodiment of the invention, finding particular utilityin a business machine, the optical character generator is comprised of alight source and an electro-optical cell wherein character images areformed by changing the polarization characteristics of a liquid crystalwhich is interposed between character electrodes. A polarizer interposedbetween the light source and the electro-optical cell polarizes thelight from the source before it impinges on the liquid crystal cell. Ananalyzer positioned to receive the polarized light passing through thecell provides an output (passes light) which has the correctpolarization angle and stops all other light. The polarization angle ofthe light passing through the liquid crystal is controlled by applying apotential across selected conductors in the cell. The light beam fromthe analyzer is then directed to a beam splitter element, which elementprovides as an output two separate beams having identicalcharacteristics. One of the beams is fed to a photothermographicelement, which element is used in conjunction with a thermal sensitivematerial to provide a permanent copy. The other beam is directed to aviewing screen for direct viewing. Means are also provided foractivating selected electrodes in the electro-optical cell to formdesired characters which means are under the control of an operator.

In a second embodiment of the present invention a matrix of lightemitting diodes are connected in circuit to an operator selector elementwhich element activates selected diodes in response to the operatorsrequest so as to form character light images. The light from theactivated diodes is directed to the beam splitter to provide the twoseparate output beams.

From the foregoing it can be seen that it is a principal object of thepresent invention to provide an improved business machine.

It is another object of the present invention to provide a printer andvisual display utilizing an optical character generator.

It is a further object of the present invention to provide a means foractivating a visual display and printer. These and other objects of thepresent invention will become more apparent when taken in conjunctionwith the following description and drawings, throughout which likereference characters indicate like parts and which drawings form a partof this application BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a blockschematic diagram of one preferred embodiment of the present invention.

FIGS. 2A, 2B, and 2C are front, back and a sectioned side view of anelectrooptical cell which may be used in the embodiment of FIG. 1',

FIGS. 3A and 3B are a top view and a sectioned view of ,aphotothermographic element which may be used in the embodiment of FIG.1;

FIGS. 4A and 4B are a bottom view and a sectioned view of a secondphotothermographic element which may be used with the preferredembodiment of FIG. 1;

FIG. 5 is a top view of a photothermographic element which may be usedin the preferred embodiment of FIG. 1;

FIG. 6 is a block diagram of a second embodiment of the invention;

FIG. 7 is the front view of an optical element which may be used withthe embodiment of FIG. 6; and

FIG. 8 is a perspective view of a business machine wherein theembodiments'of FIG. I and FIG. 6 find particular utility.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a lightsource 10, such as a tungsten bulb, powered by the power supply 26,provides a beam of light to a lens 12. The lens 12 focuses the providedbeam of light onto a polarizer 14. The polarizer polarizes the receivedbeam in a preferred plane. The polarized beam is then directed to anelectro-optical cell which may be of the field effect twisted nematictype.

A character selector 25, connected to the power supply 26, in responseto operator-activated keys 39, provides a voltage to selected areas ofthe electro-optical cell 20 so as to select a desired character. Thevoltage remains applied to the selected areas until the operator pressesa clear key. Means for accomplishing this function are well within thestate of the art and are 'not shown for purposes of clarity.

Cell 20 rotates the incident polarized light by a predetermined angle,generally 90, when there is no power applied to the cell. Under thecontrol of element selector portions of the cell have an electric fieldapplied across the liquid crystal and no longer rotate the polarizedlight. An analyzer 27 is positioned to absorb the rotated polarizedportions of the polarized beam from the electro-optical cell 20 and totransmit the nonrotated portions of the polarized beam.

The beam from analyzer 27 is directed to a beam splitting element 29,which may be a partially silvered mirror. A portion of the transmittedbeam is reflected from the beam splitter 29 on to mirror 30, with theremaining portion of the beam passing through the beam splitter to alens 32. Lens 32 focuses the beam onto a photothermographic element 33.

The character selector 25 has an output connected to aphotothermographic element power supply 37. The photothermographicelement power supply 37 is connected to the thermographic element 33 toprovide an activating voltage to the element 33 in response to a printcommand from the character selector 25. In operation, power is appliedto element 33 for a fixed period of time, approximately 500milliseconds, by the photothermographic element power supply 37 inresponse to the depression of a printout key on the character selector25. The photothermographic element 33 provides aheated patterncorresponding to the image received from lens 32.

A thermal sensitive material 40 is positioned adjacent the heated areasof element 33 for recording the generated heat image. The period of timethat a voltage is applied to element 33 is dependent somewhat on theresponse time of the thermal sensitive material, but in the 1 preferredembodiment a 500 millisecond period provided satisfactory results. Y

The beam imaged onto mirror 30 is reflected to a lens 42, which lensfocuses the beam to a viewing screen 45. The viewing screen may be madefrom any of a number of light scattering surfaces such as etched glass.

Referring to FIGS. 2A, 2B and 2C for a detailed de-' scription of theelectro-optical cell 20, a glass front plate 21 has deposited thereonsector electrodes 22 in a common numeric configuration which electrodesare transparent to light. Conductors 23 connect each of the electrodes22 to conductive tabs 15a. A glass rear plate 24 has deposited thereon acommon electrode 26. formed from a light-transparent conductive materialsuch as tin oxide, connected by a conductor 28 to a tab 15b. the tabs15a and 1512 are connected in circuit to the character selector 25. Thetwo plates 21 and 24 are positioned parallel to each other and arespaced apart by a spacer 34. Theplates and spacer are sealed together bya sealer 31 so as to form a cavity. A nematic liquid crystal material 36fills the cavity and is in electrical contact with the electrodes 22 and26.

The type of liquid crystal cell used in the preferred embodiment of thisinvention is of the Twisted Nematic Field Effect Type (sometimes calledBilevel). A basic description of the liquid crystal cell is set forth byM. Schadt and W. I-Ielfrich, in Applied Physics Letters 18 1 27 (1971).

The liquid mixture used in these cells has a positive dielectricanisotropy that is when an electric field is applied across the liquidcrystal the molecules tend to line up with their long axes parallel tothe field direction.

The composition of the nematic liquid crystal mixture for the filedeffect cell used was 40% p-methoxybenzilidine-p -butylaniline (MBBA) 40%p-ethoxybenzilidine-p-butylaniline (EBBA) 20% p-butoxybenzilidinep-aminobenzonitrile.

This mixture acts as a liquid crystal in a temperature range from 10C toC.

A field effect cell with this mixture will undergo an electro-opticswitching at about 4-12 voltsof alternating field. The distance betweenelectrodes isabout 0.5 mil. The current is in the range of microamps percharacter, and the display is readily operated directly from MOSintegrated circuits with no amplification.

The size of the liquid crystal cell is not critical. For the directreading of a number inch height is desirable, in the display. Actualcell dimensions would be typically 1 inch height and a width of 0.8 inchtimes the number of characters +1. (0.8 inch X (n+1) In operation,selected ones of the electrodes 22 and the common electrode 26 have apotential applied therebetween. The potential is selected so as toeither eliminate or change the amount of angular rotation which occursto 'the polarized light. Because the field is localized between theselected electrodes 22 and the common electrode 26, only those portionsof the liquid crystal material located between the aforementionedelectrodes will be affected. Therefore, by adjusting the angularposition of the polarizer 14 and the analyzer 27, the light transmittedthrough the liquid crystal material between the electrically activatedelectrodes will be of a different intensity from the light transmittedthrough the electrodes where no electrical field is applied. Dependingon this adjustment, either a light digit on a dark background or a darkdigit on a light background can be transmitted.

In the present embodiment, printing at the photothermographic element islight activated so a light digit is the preferred configuration.

Referring to FIGS. 3A and 3B simultaneously, the photothermographicelement 33 is shown comprised of a glass substrate 50 onto which isformed two conductors 52 and 53. The conductors 52 and 53 are configuredto be substantially parallel to each other throughout the plane of theelement. A photoconductive material 51 is deposited over and between theconductors. In operation, a potential is applied to,conductors 53 and 52so as to create a field between the conductors. Light impinging on thephotoconductive material located between the conductors causes adecrease in resistivity which in turn causes a localized current to flowbetween conductor 52 and 53, which localized current causes a localizedheating. By adjusting the spacing and the number of parallel paths percross-sectional area of the element the resolution of the localized heatpatterns can be increased or decreased as desired.

Referring to FIGS. 4A and 4B, a second photothermographic element isdisclosed wherein a glass substrate 55 has deposited thereon a meshconfigured electrode 56 having a plurality of openings 59 definedthereby. A photoconductive material 57 is deposited onto the electrode56 and into the defined openings 59. An electrode 58 is deposited ontothe photoconductive material 57. In operation, a potential is formedbetween electrodes 56 and 58. Light traversing electrode 56 andimpinging on photoconductive material 57 changes the resistivity of thephotoconductive material causing current to flow between conductors 56and 58 in a localized pattern, which current causes a localized heatingof electrode 58. Electrode 58 is positioned in close proximity to thethermal sensitive material 40 so as to effect a transfer of thelocalized heat pattern.

Referring to FIG. 5, another photothermographic element which may beused with the preferred embodiments of the invention is shown formedfrom a glass substrate 60 onto which are deposited an electrode 62 andan electrode 63. A photoconductive material 61 is deposited over andbetween the electrodes. Potentials are applied to the electrodes 62 and63 by means of conductors 64 and 65, respectively. Conductors 64 and 65are connected in circuit to the photothermographic element power supply37. When activated by a printout signal from the character selector 25,a potential field is created in the areas 66 between the electrodes 62and 63. Potential fields will occur in other areas, but no light shouldimpinge in those areas. The area 66 (between the electrodes) is asubstantial duplicate of the area formed by the seven bar elements 22used in the electro-optical cell 20.

In operation, light transmitted through the electrooptical cell impingeson the corresponding areas between the electrode 62 and the electrode63, causing a change in the resistivity of the photoconductive material,which change increases the current flowing through the photoconductivematerial within the areas onto which the light impinges, thereby causinglocalized heating of these areas. The thermal sensitive material 40 ispositioned adjacent the heated areas to allow the heat formed image tobe transferred to the material 40.

Referring to FIGS. 6 and 7, an array 70 of light emitting diodes 73 isused to generate a light pattern corresponding to an operator-selectedcharacterv Conductors 74 and 75 connect each of the diodes 73 to thecharacter selector 25 in the well-known matrix configuration. Theoperator-selected keys 39 apply the proper potentials to the column androw conductors of the matrix so as to cause the diodes 73 connected atthe crossover points of the selected row and column electrodes to emitlight. The light image formed by the array 70 is transmitted to the beamsplitter 29. The beam splitter 29 reflects a portion of the beam onto amirror 30 with the remaining portion of the beam being passed through tolens 32. Lens 32 then directs and focuses the image onto thephotothermographic element 33 similar to the first embodiment. Element33 is activated by the photothermographic element controller 37 forprinting out the image onto the thermal sensitive material 40. Mirror 30reflects the other beam to lens 42. Lens 42 in turn focuses the imageonto the viewing screen 45.

FIG. 8 illustrates a business machine (transaction terminal) wherein theviewing screen 45 is mounted for easy customer viewing and the thermalsensitive material 40, which may be a sales receipt, is shown ready fordispensing to the customer. The operator-selected keyboard 39 is shownmounted in an easily accessible posi tion on the business machine.

An amount of heat used to make the print will vary depending on thevoltage across the photothermographic element and the time allowed forthe print cycle assuming the light to be a constant. For an interdigitalphotothermographic element with 3 mil. electrodes and 6 mil. spacing(FIG. 3), typical figures would be:

Voltage across element approximately 25 volts (AC) Illuminationapproximately 200 foot candles Printing cycle time approximately 500milliseconds.

The above figures can be varied considerably but are interdependent.Print resolutions of about 6 line pairs per millimeter have beenobtained with this type of cell.

The print size would most likely be the same as that of a typewriter oran adding machine (approximately /8 inch height, 1/10 inch width, percharacter). Good resolution has been obtained in prints of this size.Characters of larger sizes could be printed. The resolution is dependenton both printing cycle time and electrode configuration. Special purposeelectrodes (FIG. 5) should give excellent resolution and print sharpnessbecause:

a. They are matched to the liquid crystal and the electrodes act aslight masks. b. The large electrodes act as heat sinks.

While there have been shown what are considered to be the preferredembodiments of the invention, it will be manifest that many changes andmodifications may be made therein without departing from the essentialspirit of the invention. It is intended, therefore, in the annexedclaims, to cover all such changes and modifications as may fall withinthe true scope of the invention.

What is claimed is:

1. Apparatus comprising, in combination:

means for forming light images;

means for directing said light images along at least two optical paths;

transducer means intercepting the image in one of said optical paths fortransforming said image into a corresponding heat image capable of beingtransferred to a heat sensitive record material;

said transducer means comprised of:

an optically transparent substrate;

a plurality of electrodes adapted to receive an electrical potentialtherebetween positioned on said optically transparent substrate, in apattern which outlines a desired composite character;

a layer of photoconductive material covering said electrodes such that alight image of a selected character impinging on the photoconductivematerial in' the electrode outlined pattern causes a change inresistance of the photoconductive material on which the light impingesthereby causing an increased temperature of said photoconductivematerial in the areas on which light impinges; and

. viewing means positioned to intercept the image in another of saidoptical paths.

2. The apparatus according to claim 1 wherein said means for directingis comprised of:

a beam splitter positioned to intercept the light images from said meansfor forming light images and for directing said light images along twooptical paths.

3. The apparatus according to claim 1 and further comprising:

means for activating said transducer means only when a heat image is tobe transferred to a heat sensitive material.

4. Apparatus comprising, in combination:

means for forming light images;

means for directing said light images along at least two optical paths;

transducer means intercepting the image in one of said optical paths fortransforming said image into a corresponding heat image capable of beingtransferred to a heat sensitive record material;

said transducer means comprised of:

an optically transparent substrate;

an electrode having a plurality of openings positioned on saidsubstrate;

a layer of photoconductive material positioned over said electrode andin said openings;

a second electrode positioned on said layer of photoconductive material,said optically transparent electrode and said second electrode adaptedto receive an electrical potential therebetween such that lightimpinging on said photoconductive material changes the resistancebetween said optically transparent electrode and said second electrodewhich in turn changes the current flow through said photoconductivematerial and the temperature of said photoconductive material; and

viewing means positioned to intercept the image in another of saidoptical paths.

5. An optical display and printer system comprising in combination:

a plurality of light sources arranged in a matrix;

means for causing selected ones of said light sources to emit light;

means for directing the image formed by said light sources along twooptical paths;

an optical-to-thermal transducer positioned to intercept the image inone of said optical paths, for transforming said optical image into acorresponding heat image which image is adapted to be transferred to aheat sensitive material, said optical-tothermal transducer comprised of:

an optically transparent substrate;

a plurality of electrodes adapted to receive an electrical potentialtherebetween positioned on said optically transparent substrate, in apattern which outlines a desired composite character;

a layer of photoconductive material over and between said electrodessuch that a light image of a selected character impinging on thephotoconductive material in the electrode outlined pattern causes achange in resistance of the photoconductive material on which the lightimpinges thereby causing an increased temperature of saidphotoconductive material in the areas on which light impinges; and

a viewing screen positioned to intercept the image in the second of saidoptical paths.

6. The optical display and printer system according to claim 5 whereinsaid optical-to-thermal transducer is comprised of:

an optically transparent substrate;

an optically transparent electrode positioned on said substrate;

a layer of photoconductive material positioned over said transparentelectrode; and

a second electrode positioned on said layer of photoconductive material,said optically transparent electrode and said second electrode adaptedto receive an electrical potential therebetween such that lightimpinging on said photoconductive material changes the resistancebetween said optically transparent electrode and said second electrodewhich in turn changes the current flow through said photoconductivematerial and the temperature of said photoconductive material.

7. The optical display and printer system according to claim 5 andfurther comprising:

means for activating said optical-to-thermal transducer only when a heatimage is to be transferred to said heat sensitive material.

8. An optical display and printer system comprising in combination:

a light source;

character image forming means positioned to intercept the light fromsaid light source, said character image forming means comprised of:

a light polarizer for receiving the light from said light source and forpolarizing the light;

a liquid crystal cell positioned to intercept the polar ized light;

means for changing the polarization characteristics of said liquidcrystal cell in selected areas so as to change the angle of thepolarized light in the selected areas;

an analyzer for passing light having a selected polarization angle;

an optical-to-thermal transducer positioned to intercept the image inone of said optical paths, for

transforming said optical image into :1 corresponding heat image whichimage is adapted to be transferred to a heat sensitive material; and

a viewing screen positioned to intercept the image in the second of saidoptical paths.

9. The system according to claim 8 wherein said liquid crystal cell isfurther comprised of:

at least one pair of electrodes, one of which electrodes of the pair isconfigured to represent a character, positioned on opposite sides ofsaid liquid crystal cell, said electrodes connected in circuit to saidmeans for changing the polarization characteristics of said liquidcrystal cell.

10. The system according to claim 9 wherein said means for changing thepolarization characteristics of said liquid crystal cell is comprisedof:

a voltage source the level of which is sufficient to change thepolarization angle of said liquid crystal cell by a desired amount; and

select means for applying the voltage from said voltage source to saidat least one pair of electrodes.

1 l. The system according to claim 9 and further comprising:

a lens interposed between said analyzer and said viewing screen forfocusing the light passed by said analyzer onto said viewing screen.

12. The system according to claim 9 wherein said means for directing theimage from said character image forming means along two optical paths isa beam splitter positioned to intercept the image from said charactergenerator.

13. An optical display and printer system comprising in-combination:

a light source;

character image forming means positioned to intercept the light fromsaid light source;

means for directing the image from said character image forming meansalong two optical paths;

an optical-to-thermal transducer positioned to intercept the image inone of said optical paths, for transforming said optical image into acorresponding heat image which image is adapted to be transferred to aheat sensitive material, said optical-tothermal transducer comprised of:

an optically transparent substrate;

a plurality of electrodes adapted to receive an electrical potentialtherebetween positioned on said optically transparent substrate, in apattern which outlines a desired composite character; and

a layer of photoconductive material covering said electrodes such that alight image of a selected character impinging on the photoconductivematerial in the electrode outlined pattern causes a change in resistanceof the photoconductive material on which the light impinges therebycausing an increased temperature of said photoconductive material in theareas on which light impinges; and

a viewing screen positioned to intercept the image in the second of saidoptical paths.

14. The optical display and printer system according to claim 13 andfurther comprising:

means for activating said optical-to-thermal transducer only when a heatimage is to be transferred to said heat sensitive material.

15. An optical display and printer system comprising in combination:

a light source;

character image forming means positioned to intercept the light fromsaid light source;

means for directing the image from said character image forming meansalong two optical paths;

an optical-to-thermal transducer positioned to intercept the image inone of said optical paths, for transforming said optical image into acorresponding heat image which image is adapted to be transferred to aheat sensitive material, said optical-tothermal transducer comprised of:

an optically transparent substrate;

an electrode having a plurality of openings positioned on saidsubstrate;

a layer of photoconductive material positioned over said electrode andin said openings;

21 second electrode positioned on said layer of photoconductivematerial, said optically transparent electrode and said second electrodeadapted to receive an electrical potential therebetween such that lightimpinging on said photoconductive material changes the resistancebetween said optically transparent electrode and said second electrodewhich in turn changes the current flow through said photoconductivematerial and the temperature of said photoconductive material; and

a viewing screen positioned to intercept the image in the second of saidoptical paths.

1. Apparatus comprising, in combination: means for forming light images;means for directing said light images along at least two optical paths;transducer means intercepting the image in one of said optical paths fortransforming said image into a corresponding heat image capable of beingtransferred to a heat sensitive record material; said transducer meanscomprised of: an optically transparent substrate; a plurality ofelectrodes adapted to receive an electrical potential therebetweenpositioned on said optically transparent substrate, in a pattern whichoutlines a desired composite character; a layer of photoconductivematerial covering said electrodes such that a light image of a selectedcharacter impinging on the photoconductive material in the electrodeoutlined pattern causes a change in resistance of the photoconductivematerial on which the light impinges thereby causing an increasedtemperature of said photoconductive material in the areas on which lightimpinges; and viewing means positioned to intercept the image in anotherof said optical paths.
 2. The apparatus according to claim 1 whereinsaid means for directing is comprised of: a beam splitter positioned tointercept the light images from said means for forming light images andfor directing said light images along two optical paths.
 3. Theapparatus according to claim 1 and further comprising: means foractivating said transducer means only when a heat image is to betransferred to a heat sensitive material.
 4. Apparatus comprising, incombination: means for forming light images; means for directing saidlight images along at least two optiCal paths; transducer meansintercepting the image in one of said optical paths for transformingsaid image into a corresponding heat image capable of being transferredto a heat sensitive record material; said transducer means comprised of:an optically transparent substrate; an electrode having a plurality ofopenings positioned on said substrate; a layer of photoconductivematerial positioned over said electrode and in said openings; a secondelectrode positioned on said layer of photoconductive material, saidoptically transparent electrode and said second electrode adapted toreceive an electrical potential therebetween such that light impingingon said photoconductive material changes the resistance between saidoptically transparent electrode and said second electrode which in turnchanges the current flow through said photoconductive material and thetemperature of said photoconductive material; and viewing meanspositioned to intercept the image in another of said optical paths. 5.An optical display and printer system comprising in combination: aplurality of light sources arranged in a matrix; means for causingselected ones of said light sources to emit light; means for directingthe image formed by said light sources along two optical paths; anoptical-to-thermal transducer positioned to intercept the image in oneof said optical paths, for transforming said optical image into acorresponding heat image which image is adapted to be transferred to aheat sensitive material, said optical-to-thermal transducer comprisedof: an optically transparent substrate; a plurality of electrodesadapted to receive an electrical potential therebetween positioned onsaid optically transparent substrate, in a pattern which outlines adesired composite character; a layer of photoconductive material overand between said electrodes such that a light image of a selectedcharacter impinging on the photoconductive material in the electrodeoutlined pattern causes a change in resistance of the photoconductivematerial on which the light impinges thereby causing an increasedtemperature of said photoconductive material in the areas on which lightimpinges; and a viewing screen positioned to intercept the image in thesecond of said optical paths.
 6. The optical display and printer systemaccording to claim 5 wherein said optical-to-thermal transducer iscomprised of: an optically transparent substrate; an opticallytransparent electrode positioned on said substrate; a layer ofphotoconductive material positioned over said transparent electrode; anda second electrode positioned on said layer of photoconductive material,said optically transparent electrode and said second electrode adaptedto receive an electrical potential therebetween such that lightimpinging on said photoconductive material changes the resistancebetween said optically transparent electrode and said second electrodewhich in turn changes the current flow through said photoconductivematerial and the temperature of said photoconductive material.
 7. Theoptical display and printer system according to claim 5 and furthercomprising: means for activating said optical-to-thermal transducer onlywhen a heat image is to be transferred to said heat sensitive material.8. An optical display and printer system comprising in combination: alight source; character image forming means positioned to intercept thelight from said light source, said character image forming meanscomprised of: a light polarizer for receiving the light from said lightsource and for polarizing the light; a liquid crystal cell positioned tointercept the polarized light; means for changing the polarizationcharacteristics of said liquid crystal cell in selected areas so as tochange the angle of the polarized light in the selected areas; ananalyzer for passing light having a selected polarization angle; anoptical-to-thermal transducer positioned to intercept the image in oneof said optical paths, for transforming said optical image into acorresponding heat image which image is adapted to be transferred to aheat sensitive material; and a viewing screen positioned to interceptthe image in the second of said optical paths.
 9. The system accordingto claim 8 wherein said liquid crystal cell is further comprised of: atleast one pair of electrodes, one of which electrodes of the pair isconfigured to represent a character, positioned on opposite sides ofsaid liquid crystal cell, said electrodes connected in circuit to saidmeans for changing the polarization characteristics of said liquidcrystal cell.
 10. The system according to claim 9 wherein said means forchanging the polarization characteristics of said liquid crystal cell iscomprised of: a voltage source the level of which is sufficient tochange the polarization angle of said liquid crystal cell by a desiredamount; and select means for applying the voltage from said voltagesource to said at least one pair of electrodes.
 11. The system accordingto claim 9 and further comprising: a lens interposed between saidanalyzer and said viewing screen for focusing the light passed by saidanalyzer onto said viewing screen.
 12. The system according to claim 9wherein said means for directing the image from said character imageforming means along two optical paths is a beam splitter positioned tointercept the image from said character generator.
 13. An opticaldisplay and printer system comprising in-combination: a light source;character image forming means positioned to intercept the light fromsaid light source; means for directing the image from said characterimage forming means along two optical paths; an optical-to-thermaltransducer positioned to intercept the image in one of said opticalpaths, for transforming said optical image into a corresponding heatimage which image is adapted to be transferred to a heat sensitivematerial, said optical-to-thermal transducer comprised of: an opticallytransparent substrate; a plurality of electrodes adapted to receive anelectrical potential therebetween positioned on said opticallytransparent substrate, in a pattern which outlines a desired compositecharacter; and a layer of photoconductive material covering saidelectrodes such that a light image of a selected character impinging onthe photoconductive material in the electrode outlined pattern causes achange in resistance of the photoconductive material on which the lightimpinges thereby causing an increased temperature of saidphotoconductive material in the areas on which light impinges; and aviewing screen positioned to intercept the image in the second of saidoptical paths.
 14. The optical display and printer system according toclaim 13 and further comprising: means for activating saidoptical-to-thermal transducer only when a heat image is to betransferred to said heat sensitive material.
 15. An optical display andprinter system comprising in combination: a light source; characterimage forming means positioned to intercept the light from said lightsource; means for directing the image from said character image formingmeans along two optical paths; an optical-to-thermal transducerpositioned to intercept the image in one of said optical paths, fortransforming said optical image into a corresponding heat image whichimage is adapted to be transferred to a heat sensitive material, saidoptical-to-thermal transducer comprised of: an optically transparentsubstrate; an electrode having a plurality of openings positioned onsaid substrate; a layer of photoconductive material positioned over saidelectrode and in said openings; a second electrode positioned on saidlayer of photoconductive material, said optically transparent electrodeand said second elecTrode adapted to receive an electrical potentialtherebetween such that light impinging on said photoconductive materialchanges the resistance between said optically transparent electrode andsaid second electrode which in turn changes the current flow throughsaid photoconductive material and the temperature of saidphotoconductive material; and a viewing screen positioned to interceptthe image in the second of said optical paths.